The present invention relates to corrugated product dryers. More particularly, the present invention relates to dryers that draw air through corrugations in the corrugated product, often referred to as "corrugated board".
Corrugated product is formed by gluing corrugated medium in between two corrugated liners. The corrugated product is strong and lightweight and is used for many purposes including boxes, shipping containers and trays.
When the corrugated product is initially produced, it is very hot and very wet. Currently, corrugated product is held in inventory for approximately eight to twelve hours to allow the product to cool and dry before it can be moved down the production line for subsequent operations. These subsequent operations include cutting and folding the corrugated product into a final product form such as shipping containers or trays and printing on the corrugated product.
Another subsequent operation that may take place is the application of hot wax curtain coating. Excess heat in the corrugated product causes the curtain coated wax to saturate into the corrugated product rather than laying wax on the surface of the product. Curtain coated wax needs to lay on the surface of the corrugated product to form an effective moisture barrier when the corrugated product is used as a shipping container to ship perishable items.
White or colored liners are used to produce corrugated product when greater aesthetics is required. These white or colored liners can become discolored when heat carries wax from the medium or moisture, from the glue used to bond the corrugated medium to the liner, through the liner. The longer the corrugated product stays hot and wet, the greater the possibility that the liners may be discolored.
The eight to twelve hour storage time required to allow the corrugated product to cool before it is transferred to these subsequent processes requires a lot of floor space which complicates material handling and occupies space that may be used for production. The long storage time of the hot and wet corrugated product also contributes to the discoloration of the special white and colored liners.
What is needed is a corrugated product dryer that cools and dries corrugated product very quickly. This dryer would reduce the warehouse space it takes to house the hot and wet corrugated product while it is cooling and drying.
In accordance with the present invention, a corrugated product dryer includes an airflow duct, a fan situated in the airflow duct, and a plenum having a first side in airflow communication with the airflow duct and an open second side facing toward the corrugated product during the drying process.
Advantageously, the fan draws airflow through the corrugated product and into the plenum. The airflow then travels through the airflow duct where it is exhausted out of the dryer. The airflow is drawn through the corrugated product through gaps or flutes formed between the liner and corrugated medium.
In preferred embodiments of the present invention, the fan and plenum are sized to create a uniform pressure across the second side of the plenum facing the corrugated product. This uniform pressure permits an approximately equal airflow to flow through all portions of the corrugated product.
Illustratively, the plenum includes a side wall defining an open-faced chamber opening towards the corrugated product and the dryer further includes bristles appended to the side wall and facing toward the dryer. The corrugated product abuts against the bristles so that a gap between the dryer and corrugated product does not form. If such a gap were allowed, airflow would enter the plenum through the gap and not through the corrugated product.
Additional features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.